1. Field of the Invention
This invention relates to an intraocular lens (substitute for human lens) having a coating layer formed on its surface and to a method of manufacturing this type of lens.
2. Description of the Prior Art
Conventionally, in the treatment of cataracts, the clouded lens is enucleated by surgery, and an artificial lens is implanted in the capsula lentis, thereby enabling recovery of vision after the operation. Use of the in-the-bag method which is considered to enable implantation of such an intraocular lens with fewer complications, namely, the method of inserting the intraocular lens in the capsula lentis, is now becoming a mainstream practice.
Ordinarily, this type of intraocular lens is formed of a material constituted mainly by polymethyl methacrylate, while a lens support called harptic is formed of a material such as polymethyl methacrylate, polyvinylidene fluoride or the like.
With respect to this conventional intraocular lens, problems are encountered due to a free monomer of polymethyl methacrylate which oozes out and permeates the eye.
U.S. Pat. No. 4,312,575 is directed to an intraocular lens designed to form a coating on its surface by plasma polymerization in order to prevent the flow of a free monomer into the eye.
U.S. Pat. No. 4,312,575 also states that a coloring material may be mixed in the base material of an intraocular lens before application of the coating layer in order to adapt the lens to absorb ultraviolet rays harmful to the retina.
However, mixing an ultraviolet ray absorbing substance in the base material of the intraocular lens reduces the mechanical strength of the lens.